This is a multicenter, randomized, double-blind, placebo controlled, 24 month study with 6 and 12 month interim analyses to evaluate the efficacy, safety, and tolerability of weekly oral Alendronate 70 mg on alveolar crestal height and clinical attachment level in men and women with moderate to severe periodontal disease in the absence of scaling and root planning. Disease progression will be frequently monitored and mechanical therapy administered if clinically indicated. Eligible patients will be randomly allocated to 1 of 2 treatment groups.